Accounting of weathering enhancement by mafic mineral spreading for CO ₂ storage

The reduction of atmospheric CO 2 is an urgent global issue in the mitigation of global warming. Carbonate acts as a carbon sink in Earth's surface layer, and the weathering of terrestrial silicates and the deposition of oceanic calcium carbonate and organic matter mainly determine atmospheric and oceanic carbon dynamics on geological timescales. Various CO 2 -reduction approaches have been evaluated and the weathering-acceleration method is expected to be a low-cost approach. This study attempts to estimate carbonate precipitation potential and the dissolution rate from alkali leaching rates using weathering tests on mafic rocks. Based on Japan's annual average rainfall, the in situ carbonate precipitation potential obtained by spreading an olivine mineral or basalt rock powder at 40 tonne-powder ha –1 was of the order of 10 −3 tonne yr –1 tonne-rock –1 . This weathering rate could not be greatly accelerated under natural temperature conditions and fine granulation of the minerals.